We propose an object-oriented calculus with internal concurrency and class-based inheritance that is built upon the join calculus. Method calls, locks, and states are handled in a uniform manner, using asynchronous messages. Classes are partial message definitions that can be combined and transformed. We design operators for behavioral and synchronization inheritance. We also give a type system that statically enforces basic safety properties. Our model is compatible with the JoCaml implementation

Abstract not found

The ambient logic has been proposed for expressing properties of process mobility in the calculus of Mobile Ambients (MA), and as a basis for query languages on semistructured data. To understand the extensionality and the intensionality of the logic, the equivalence on MA processes induced by the logic (=L) is compared with the standard MA behavioural equivalence and with structural congruence (an intensional equivalence, used as an auxiliary relation in the definition of satisfaction of the logic). The main contributions include a co-inductive characterisation of =L as a form of labelled bisimilarity, and axiomatisations of =L on the synchronous and asynchronous (finite) calculus. The study shows that, surprisingly, the logic allows us to observe the internal structure of the processes at a very fine-grained detail, much in the same way as structural congruence does. A spin-off of the study is a better understanding of behavioural equivalence in Ambient-like calculi. For instance, behavioural equivalence is shown to be insensitive to stuttering phenomena originated by processes that may repeatedly enter and exit an ambient.

Abstract not found

Abstract not found

Abstract One way of enforcing an information flow control pol-icy is to use a static type system capable of guaranteeing a noninterference property. Noninterference requires thattwo processes with distinct "high"-level components, but common "low"-level structure, cannot be distinguished by"low"-level observers. We state this property in terms of a rather strict notion of process equivalence, namely weakbarbed reduction congruence. Because noninterference is not a safety property, it isoften regarded as more difficult to establish than a conventional type safety result. This paper aims to providean elementary noninterference proof in the setting of the ss-calculus. This is done by reducing the problem to sub-ject reduction- a safety property- for a nonstandard, but fairly natural, extension of the ss-calculus, baptized the hssi-calculus. 1

E-mail: versari (at) cs.unibo.it Abstract P systems are theoretical computing devices abstracted away from the biological architecture of the cell, introduced some years ago by Gheorghe P*aun and now intensely studied. In the area of concurrent systems, process calculi have recently been applied and extended with similar aim, to simulate (and formalise) the behaviour of the cell. Although many common points can be found between the two approaches, no formal and exhaustive comparison has been carried out yet. ss @ is a new calculus, strongly ss-Calculus based, well-suited to easily encode biologically inspired process calculi. In this paper the encoding in ss @ of one variant of P systems is proposed, thus allowing a better understanding of similarities between P systems and bio-inspired process calculi.